A man facing capital murder charges for plowing his car into a crowd at the South by Southwest (SXSW) festival in Austin last month, killing four and injuring nearly two dozen others, has been charged with an additional 20 counts of aggravated assault.

Prison records posted on Tuesday show Rashad Charjuan Owens, 21, from Killeen, Texas, has had the charges of aggravated assault with a deadly weapon added to his detention booking.

Each count of aggravated assault with a deadly weapon can bring up to life in prison while a conviction on capital murder carries the possibility of the death penalty.

Lawyers for Owens, currently held on a $3 million bond, have not been available for comment.

Police said Owens fled from a sobriety checkpoint on March 13, smashed through a police barricade and then mowed down people, some of them lined up outside a nightclub, as he sped through several city blocks.

Jamie West, 27, from Austin, and Steven Craenmehr, 35, of Amsterdam in the Netherlands, died at the scene.

Sandy Thuy Le, 26, who moved from Mississippi to Austin, died about a week later from injuries sustained in the incident and DeAndre Tatum, 18 and from Fort Worth died last week.

South by Southwest, which ran from March 7-16, began as a music event in 1987. It features technology conferences, a film festival and music shows that draw tens of thousands of people to the Texas capital annually.